Transformer for operating electric



Aug. 7, .1951

M uncommon A. E. FEINBERG 2,563,595

TRANSFORMER FOR OPERATING ELECTRIC DISCHARGE TUBES Filed Sept. 21, 1949 fins. Z 13 2 I l I20 AC IN V EN TOR. alber'i E Feinberg Patented Aug. 7, 1951 TRANSFORMER FOR OPERATING ELECTRIC DISCHARGE TUBES Albert E. Feinberg, Chicago, Ill., assignor to Advance Transformer (30., Chicago, 111., a corporation of Illinois Application September 21, 1949, Serial No. 116,947

'11 Claims.

This invention relates to transformers for furnishing the filament heating current for a hot cathode electric discharge tube and for furnishing also the discharge current for the tube.

It is one of the objects of the present invention to provide a .transformer for the above mentioned purposes which will automatically regulate the filament voltage and current as the requirements change in going from starting conditions to normal operating conditions, and which will automatically regulate the applied ignition voltage as the requirements change from the high initial voltage required to start the discharge to the lower voltage required after the glow discharge has started.

It is a further object of the present invention to provide a transformer'which will operate a hot cathode electric discharge device in the manner above set forth when connected thereto, without requiring any additional external equipment.

It is another object of the present invention to provide a transformer of the above mentioned character which will be quite compact and which will be economical of construction and eflicient in operation.

It is a still further object of the present invention to provide a transformer of the above character which will provide sufficient filament current to cause a very quick start of the glow discharge and which will thereafter immediately reduce the filament current to a low value to prolong the life of the filament.

In the preferred embodiment of the present invention the filament voltage is obtained from two series connected transformer coils which are so located on the core that the voltage of one of them is determined by the flux through the transformer primary, the voltage of the other being determined by the flux through the transformer secondary. The coils are connected so that their voltages are additive uponenergization of the transformer primary and before the secondary is furnishing any ignition current. When ige nition takes place lamp current flows through the secondary. The secondary fiux actually substantially reverses itself so that the voltages of the two filament coils are then out of phase approximately 160.

The attainment of the above and further objects of the present invention will be appar nt from the following specification taken in conjunction with the accompanying drawing forming a part thereof.

In the drawing:

Figure 1 is a diagrammatic view of a transformer constructed in accordance with the principles of the present invention; and

Figure 2 is a circuit diagram showing the connections of that transformer to a hot cathode lamp.

In the accompanying drawing like reference numerals designate like parts throughout.

The transformer of the present invention, indicated in general by the reference numeral I, includes a conventional shell type magnetic structure comprising open rectangular laminations 2 stacked to form a group of sufilcient thickness, and a stack of core laminations 3 on which are mounted the transformer coils and which core laminations 3 with the windings assembled thereon are then positioned in the shell laminations 2 to provide substantially no gap at the abutting joints 4-5, and to provide magnetic shunts 66 for leakage flux from the core 3 to the longitudinal sides 7-! of the shell 2 substantially midway of the length of the transformer, which shunts include equal air gaps 8-9. These air gaps are of a combined thickness of the order of .035 inch. This is a standard shell type magnetic structure for transformers that supply current to hot cathode type of fluorescent lamps.

The coils of the transformer include a group of primary coils I0 and a similar but not identical group of secondary coils II. The primary coil group I0 includes a primary coil or winding I2 and two auxiliary coils I3 and II concentric therewith. The coils I2, I3 and I4 are all wound in the same direction, the primary coil I2 being on the inside and surrounded by the coil I3 which in turn is surrounded by the coil I4. The coils I2, I3 and M are suitably insulated for the voltages encountered. The secondary coil assembly II likewise includes a central secondary coil I5 surrounded by an auxiliary coil l6 which in turn is surrounded by another auxiliary coil II, the three coils being all wound in the same direction and suitably insulated for the voltages encountered. In one preferred construction the primary coil I2 had 780 turns and the auxiliary coils I3 and I4 each had turns, the three coils being of number 27 wire. In that same construction the secondary I5 had 840 turns and the auxiliary coils I6 and I1 each had turns, those three coils being of number 28 wire.

The primary I2 is connected to a source of 60 cycle alternating current. The primary auxiliary coil l3 and the secondary auxiliary coil I1 are connected in series and supply heating current to the heating filament 20 of a conventional filament type hot cathode fluorescent lamp 2 I. The primary auxiliary coil I4 and the secondary auxiliary coil I 8 are connected in series and supply heating current to the heating'filament 22 of the lamp 2|. The secondary I is connected in step-up auto transformer relationship with the primary I2 and supplies the ignition current for the lamp 2 I.

Before ignition takes place in the lamp, that is. when the cathodes 24-25 of the lamp are open circuited, the voltages of the coils I2 and I3 are additive and the voltages of the coils I5 and I6 are additive. The voltage of the-coil I4 is additive to the voltages of the coils I 5 and I6, and the voltage of the coil I! is additive to thevoltage of the coils I3 and I 2. It is thus apparent that the voltage applied to the filament 20 is-the sum of the voltages induced in the coils I4 and I1, which voltages are substantially in phase, and the voltage applied to the filament 22 is the sum of the voltages induced in the coils I4 and I6, which voltages are also substantially in phase. In the construction above set forth the voltages induced in each of the coils I3 and I4 was of the order of seven volts, and the voltages induced n each of the coils I6 and I! was in each case of the order of eight volts before ignition takes place between the cathodes 24-25. After ignition takes place the voltages across the coils I3, I4, I6 and I7 drop in each case to of the order of six and three-quarters volts. However, after lamp ignition takes place and lamp current flows between the cathodes, the secondar flux actually substantially reverses itself so that the voltages in the coils I6 and II are approximately 160 out of phase with the voltages in the coils I3 and I4. Because of the phase displacement the vector sum of the voltages of the coils I3 and I 6 or of the coils I4 and I! now drops to approximately 2.5 volts. As a result the filament current drops from the previous value of approximately .8 ampere to approximately /6 of that amount.

The magnetic shunts 6-6 are of substantially no efiect prior to the time that ignition takes place between the electrodes 24-25 .of the lamp M. This is due to the fact that the flux density in the entire iron structure of the transformer is at a value sufliciently below saturation that the reluctance of the air gaps 8-9 prevents any appreciable portion of the fiux to leak across the shunts 6-6. However, after ignition takes place between the electrodes and the direction of the secondary flux substantially reverses itself the flux relationship in the central core le 3 changes 4 eludes one primary auxiliary winding and one secondary auxiliary winding connected with their voltages additive when the secondary coil is under no load, and a magnetic structure for the coils, said magnetic structure including a magnetic shunt between the two coils for facilitating leakage flux paths for the coils.

2. A transformer for supplying current to a hot cathode electric discharge tube comprising a primary coil and a secondary coil connected in step up auto transformer relationship, the primary and the secondary each having two auxiliary windings concentric therewith, the four auxiliary windings bein connected in two series circuits each of which includes one primary auxiliary winding and one secondary auxiliary winding connected with their voltages additive when the secondary coil is under no load, and a magnetic structure for the coils, said magnetic structure including a magnetic shunt between the two coils for facilitating leakage flux paths for the calls.

3. A transformer for supplying current to a hot cathode electric discharge tube comprising a first group of three concentric coils including a, primary coil and two auxiliary coils, a second group I of three concentric coils including a secondary so that the reluctance of the small air gap 6-6 is now no longer of tremendously greater value than the reluctance of the magnetic flux path through the secondary coil sections, and as a result a substantial amount of leakage flux passes through the shunts 6-6 and the air gaps 8-9 thereby permitting reversal of the magnetic flux at the secondary end of the transformer.

In compliance with the requirements of the patent statutes I have here shown and described a preferred embodiment of my invention. It is, however, to be understood that the invention is not limited to the precise construction here shown, the same being merel illustrative of the principles of the invention. What I consider new and desire to secure by Letters Patent is:

l. A transformer for supplying current to a hot cathode electric discharge tube comprising a primary coil and a secondary coil connected in step up auto transformer relationship, the primary and the secondary each having two auxiliary windings, the four auxiliary windings being connected in two series circuits each of which inand two auxiliary coils, a magnetic coupling for the two groups of coils, the auxiliary coils of the two groups being connected in two circuits each of which includes one auxiliary coil of one group and one auxiliary coil of the other group connected in series with their voltages additive when the secondary coil is carrying substantially no load.

4. A transformer for supplying current to a hot cathode electric discharge tube comprising a first group of three concentric coils including a, primary coil and two auxiliary coils, a second group of three concentric coils including a secondary and two auxiliary coils, the coils of the second group having each a larger number of turns than the coils of the first group, a magnetic coupling for the two groups of coils, the coupling including a magnetic flux shunt path between the two groups of coils which shunt path has an air gap therein, the auxiliary coils of the two groups being connected in two circuits each of which includes one auxiliary coil of one group and one auxiliary coil of the other group connected in series with their voltages additive when the secondary coil is carrying substantially no load.

5. A transformer for supplying current to a hot cathode electric discharge tube comprising a first group of coils including a primary coil and two auxiliary coil windings, a second group of coils including a secondary coil and two auxiliary coils, a magnetic structure magnetically coupling the two groups of coils in a closed magnetic circuit and including a magnetic shunt between the two groups of coils for increasing leakage reactance between them, the auxiliary coils of the two groups being connected in two circuits each of which includes one auxiliary coil of one group and one auxiliary coil of the other group connected in series and with their voltages additive when the secondary coil is carrying substantially no current so that when the secondary carries its full load the voltages induced in the auxiliary coils of the secondary group are substantially reversed thereby reducing the voltages across each of the two series circuits.

6. A transformer for supplying current to a hot cathode electric discharge tube comprising a first group of coils including a primary coil and two aseasos auxiliary coil windings, a second group of coils including a secondary coil and two auxiliary coils, a magnetic structure magnetically coupling the two groups of coils in a closed magnetic circuit and including a magnetic shunt between the two oups of coils for increasing leakage reactance between them, said shunt including an air gap to minimize the effect of the shunt at low flux densities, the auxiliary coils of the two groups being connected in two circuits each of which includes one auxiliary coil of one group and one auxiliary coil of the other group connected in series and with their voltages additive when the secondary coil is carrying substantially no current so that when the secondary carries its full load the voltages induced in the auxiliary coils of the secondary group are substantially reversed thereby reducing the voltages across each of the two series circuits.

7. A transformer for supplying filament current and ignition current to a hot cathode electric discharge tube, said transformer including a magnetic structure having thereon a primary coil and a secondary coil coupled thereto for supplying ignition current to a tube and having a pair of auxiliary coils for supplying filament current to a tube, one of the auxiliary coils being located to be linked by magnetic flux in a direction determined by the direction of the magnetic flux through the primary coil and the other auxiliary coil being located to be linked by magnetic flux in a direction determined by the direction of the I magnetic flux through the secondary coil, the two auxiliary coils being connected in a series circuit with their voltages additive when the secondary is under substantially no load.

8. A transformer for supplying filament current and ignition current to a hot cathode electric discharge tube, said transformer including a magnetic structure having thereon a primary coil and a secondary coil coupled thereto for supplying, ignition current to a tube and having a pair of auxiliary coils associated with the primary coil and a pair of auxiliary coils associated with the secondary coil, the auxiliary coils being connected in two series circuits each of which includes one of the primary auxiliary coils and one of the secondary auxiliary coils, each circuit being adapted to furnish filament current to one of the filaments of a two filament hot cathode discharge tube, one of the pairs of auxiliary coils being located to be linked by magnetic flux in a direction determined by the direction of the magnetic flux through the primary coil and the other pair of auxiliary coils being located to be linked by magnetic fiux in a direction determined by the direction of the magnetic flux through the secondary coil, the two auxiliary coils of each series circuit being connected with their voltages additive {when the secondary is under substantially no oad. Y

9. A shell type transformer for supplying filament current and ignition current to a hot cathode electric discharge tube. said transformer comprising a magnetic structure having two longitudinal sides joined by two transverse sides and a longitudinal core extending from one transverse side to the other between the two longitudinal sides, a first group of transformer coils on the core and including a primary coil and two auxiliary coils, a second group of transformer coils on the core and including a secondary coil and two auxiliary coils, the magnetic structure including a magnetic shunt between the two groups of coils with a gap in the shunt path but outside of the path of the primary magnetizing flux, the secondary supplying the ignition current and the auxiliary coils supplying the filament current, the auxiliary coils being connected in two circuits each of which includes one auxiliary coil of one group and one auxiliary coil of the other group connected with their voltages additive.

10. A shell type transformer for supplying filament current and ignition current to a hot cathode electric discharge tube, said transformer comprising a magnetic structure having two longitudinal sides Joined by two transverse sides and a longitudinal core extending from one transv verse side to the other between the two longitudinal sides, a first group of concentric transformer coils on the core and including a primary coil and two auxiliary coils, a second group of concentric transformer coils on the core and including a secondary coil and two auxiliary coils, the magnetic structure including a magnetic shunt between the two groups of coils with a gap in the shunt path but outside of the path of the primary magnetizing flux, the secondary supplying the ignition current and the auxiliary coils supplying the filament current, the auxiliary coils being connected in two circuits each of which includes one auxiliary coil of one group and one auxiliary coil of the other group connected with their voltages additive.

11. A shell type transformer for supplying filament current and ignition current to a hot cathode electric discharge tube, said transformer comprising a magnetic structure having two longitudinal sides joined by two transverse sides and a longitudinal core extending from one transverse side to the other between the two longitudinal sides, a first group of transformer coils on the core and including a primary coil and two auxiliary coils surrounding the primary coil, 9. second group of transformer coils on the core and including a secondary coil and two auxiliary coils surrounding the secondary coil, the magnetic structure including a magnetic shunt between the two groups of coils with a gap in the shunt path but outside of the path of the primary magnetizing fiux, the secondary supplying the ignition current and the auxiliary coils supplying the filament current, the auxiliary coils being connected in two circuits each of which includes one auxiliary coil of one group and one auxiliary coil of the other group connected with their voltagu additive.

ALBERT E. FEINBERG.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,126,787 Le Bel Aug. 16, 1938 2,446,033 Wellings July 27, 1948 2,509,188 Feinberg May 23. 1950 

